U.S. patent application number 11/652123 was filed with the patent office on 2007-07-19 for repaired extrider dies and repairing method therefor.
This patent application is currently assigned to Denso Corporation. Invention is credited to Hitoshi Kanmura.
Application Number | 20070164456 11/652123 |
Document ID | / |
Family ID | 38262438 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070164456 |
Kind Code |
A1 |
Kanmura; Hitoshi |
July 19, 2007 |
Repaired extrider dies and repairing method therefor
Abstract
A method is provided for repairing a die for molding a
structure. A die to be repaired has holes for supplying a material,
grooves arranged in a lattice form for communicating with the
respective holes and for forming the material into a desired shape,
and worn-out portions caused by repeated use. In the method, a
repairing film is formed on a surface having the grooves and
serving as an end face of a die body, through which extrusion is
performed, so as to extend onto each corner at an intersecting line
between the groove-formed surface and an inner side face of each
groove, to restore each worn-out portion. Meanwhile, a material is
supplied from the groove-formed surface side utilizing either one
or both of PVD and CVD processes. This method readily provides a
repaired die with good accuracy, which is excellent in durability
and abrasion resistance.
Inventors: |
Kanmura; Hitoshi;
(Inabe-gun, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
Denso Corporation
Kariya-city
JP
|
Family ID: |
38262438 |
Appl. No.: |
11/652123 |
Filed: |
January 11, 2007 |
Current U.S.
Class: |
257/787 ;
438/124 |
Current CPC
Class: |
C23C 16/042 20130101;
B28B 3/269 20130101; C23C 14/042 20130101 |
Class at
Publication: |
257/787 ;
438/124 |
International
Class: |
H01L 23/28 20060101
H01L023/28; H01L 21/00 20060101 H01L021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2006 |
JP |
2006-006644 |
Jan 13, 2006 |
JP |
2006-006645 |
Claims
1. A method for repairing a used extrusion die being used to form a
structural body, the die having a first surface, a lattice-shaped
groove thereon, a through-hole which communicates with the groove,
and a worn-out corner where the first surface crosses an inner wall
of the groove, the method comprising steps of; supplying a material
to the first surface; and forming a film on the worn-out corner
with the material.
2. The method recited in claim 1, wherein the forming step forms
the film on the inner wall to reach a depth less than one tenth
depth of the groove from a level of the first surface.
3. The method recited in claim 1, wherein the forming step is
performed using a physical vapor deposition (PVD) process.
4. The method recited in claim 3, further comprising a masking step
before the supplying step, the masking step masking a second
surface which communicates the hole.
5. The method recited in claim 3, wherein the forming step forms a
single-layered film or a multi-layered film composed of CrN and/or
TiN.
6. The method recited in claim 1, wherein the forming step is
performed using a chemical vapor deposition (CVD) process.
7. The method recited in claim 6, further comprising a masking step
before the supplying step, the masking step masking a second
surface which communicates the hole.
8. The method recited in claim 6, wherein the forming step forms a
single-layered film or a multi-layered film composed of at least
one selected from the group consisting of TiC, TiCN, and TiN.
9. The method recited in claim 1, wherein the forming step
comprises; first forming step for forming a first film using a
chemical vapor deposition process; and second forming step for
forming a second film on the first film using a physical vapor
deposition process.
10. A method for manufacturing an extrusion die which is used to
extrusion-mold a structural body, the die having an surface with a
groove thereon, a through-hole communicating with the groove, and a
corner where the surface crosses a wall of the groove, the method
comprising; rounding for rounding the corner; and forming for
forming a film on a rounded corner rounded by the rounding
step.
11. A die for extrusion-molding a structural body comprising: a
surface with a groove thereon; a through-hole communicating with
the groove; a rounded corner of the die, the corner where the
surface crosses a wall of the groove; and a film being formed on
the corner.
12. The die recited in claim 11, wherein the film reaches a depth
less than one tenth depth of the groove from the surface.
13. The die recited in claim 11, wherein the film is a
single-layered film or a multi-layered film composed of at least
one selected from the group consisting of TiN, CrN, TiC, TiCN, and
TiN.
14. The die recited in claim 11, wherein hardness of the film is
harder than hardness of the body.
15. The die recited in claim 11, wherein hardness of the film is
equal to or one and half harder than hardness of the body.
16. The die recited in claim 11, wherein hardness of the film is
harder than 500 HV.
17. The die recited in claim 11, wherein hardness of the film is
equal to or harder than 750 HV.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on and claims the benefit of
priorities from earlier Japanese Patent Application Nos.
2006-006645 and 2006-006644 both filed on Jan. 13, 2006, the
descriptions of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Technical field of the Invention
[0003] The present invention relates to a method for repairing a
die for molding a structure utilizing a process of extrusion, and a
die repaired by using the repairing method.
[0004] 2. Related Art
[0005] A ceramic honeycomb structure used as an exhaust gas
clarifying filter for a vehicle, for example, is manufactured by
extruding a material containing a ceramics material by using a die
for molding a honeycomb structure (hereinafter referred to simply
as a "die").
[0006] Such a die is provided in its body with holes for supplying
a material, and grooves arranged in a lattice form for
communicating with the supply holes and for molding the material
into a honeycomb shape.
[0007] When a material is extruded using the die mentioned above,
the material flowing through the supply holes and the grooves comes
into contact with the die body to produce friction therebetween.
The friction produced in this way causes abrasion in the die body.
In particular, each corner formed at an intersecting line between a
surface where the groove is formed and an inner surface of each
groove is likely to suffer from abrasion. Repetition of extrusion
may enlarge the portion worn out by the abrasion to deteriorate the
dimensional accuracy of the extruded honeycomb structure. Thus,
when the dimensional error of the extruded honeycomb structure
exceeds a design tolerance, the life of the die comes to an
end.
[0008] Some methods for repairing a die that has ended its lifetime
have been suggested. For example, one repairing method uses
electroless nickel plating or hard chromium plating, for example,
for treatment of an abrasion portion in a die body. In this case,
however, abrasion resistance of the portion treated with such
plating is likely to become insufficient.
[0009] In order to achieve sufficient abrasion resistance, one
method uses a CVD process to form a film having abrasion resistance
over the entire surface of a die body (refer to U.S. Pat. Nos.
5,256,449 and 5,328,513 (which are both based on Japanese Patent
Laid-Open No. H05-269719)). However, it is difficult to form a film
of an even thickness over the entire surface of a die body using a
CVD process. Thus, a repaired die tends to suffer from insufficient
dimensional accuracy without being able to obtain a honeycomb
structure with a desired dimension.
[0010] In this way, the conventional methods for repairing dies had
difficulty in readily repairing a die with an accurate dimension.
Further, a die repaired in this way may not have sufficient
durability or abrasion resistance.
SUMMARY OF THE INVENTION
[0011] The present invention has been made in light of the problems
provided above, and has as its object to provide a method for
repairing a die for molding a structure and to provide a die
repaired using the repairing method, which is able to readily and
accurately repair a die that has been disabled, through repeated
use, to exert accuracy finishing required by a structure to be
molded, and which ensures excellent durability and abrasion
resistance.
[0012] The present invention provides, as one aspect, a method for
repairing a used extrusion die being used to form a structural
body, the die having a first surface, a lattice-shaped groove
thereon, a through-hole which communicates with the groove, and a
worn corner where the first surface crosses an inner wall of the
groove, the method comprising steps of supplying a material to the
first surface, and forming a film on the worn corner with the
material.
[0013] The present invention provides, as another aspect, a method
for manufacturing an extrusion die which is used to extrusion-mold
a structural body, the die having a surface with a groove thereon,
a through-hole communicating with the groove, and a corner where
the surface crosses a wall of the groove, the method comprising
steps of rounding for rounding the corner, and forming for forming
a film on a rounded corner rounded by the rounding step.
[0014] The present invention provides, as still another aspect, a
die for extrusion-molding a structural body comprising a surface
with a groove thereon, a through-hole communicating with the
groove, a rounded corner of the die, the corner where the surface
crosses a wall of the groove, and a film being formed on the
corner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the accompanying drawings:
[0016] FIG. 1 is a partial perspective sectional view showing a
structure of a die before use, according to first, second and third
embodiments of the invention;
[0017] FIG. 2 is a sectional view taken along line II-II' of FIG.
1;
[0018] FIG. 3 is a sectional view (i.e. an enlarged view of part
III of FIG. 2 after use) showing a vicinity of a groove of a die to
be repaired, according to the first to the third embodiments of the
invention;
[0019] FIG. 4 is an explanatory view showing a state where the a
die has been secured to a PVD jig, according to the first to the
third embodiments;
[0020] FIG. 5 is an explanatory view showing an arrangement of a
PVD apparatus, according to the first to the third embodiments of
the invention;
[0021] FIG. 6 is a sectional view showing a vicinity of a groove of
a repaired die, according to the first and the second embodiments
of the invention;
[0022] FIG. 7 is a diagram explaining a relation between a depth
"d" from a groove-formed surface along a direction in which a
groove extends, and a thickness "t" of a CVD repairing film and a
PVD repairing film, according to the first embodiment of the
invention;
[0023] FIG. 8 is a diagram explaining a relation between a distance
L from an inner side face of a groove along a direction in which a
groove-formed surface extends, and a thickness "s" of a CVD
repairing film and a PVD repairing film, according to the first
embodiment of the invention;
[0024] FIG. 9 is an explanatory view showing a state where a die
has been secured to a CVD jig, according to the second and third
embodiments of the invention;
[0025] FIG. 10 is an explanatory view showing an arrangement of a
CVD apparatus, according to the second and third embodiments of the
invention;
[0026] FIG. 11 is an explanatory view showing a vicinity of a
groove of a repaired die, according to the third embodiment of the
invention;
[0027] FIG. 12 is a diagram explaining a relation between a depth
"d" from a groove-formed surface along a direction in which a
groove extends, and a thickness "t" of a repairing film, according
to the third embodiment of the invention;
[0028] FIG. 13 is a diagram explaining a relation between a
distance L from an inner side face of a groove along a direction in
which a groove-formed surface extends, and a thickness "s" of a
repairing film, according to the third embodiment of the
invention;
[0029] FIG. 14 is an explanatory view showing a state where a die
has been secured to a CVD jig, according to a modification of the
third embodiment of the invention;
[0030] FIG. 15 is an explanatory view showing a state where a die
has been secured to a PVD jig, according to the modification of the
third embodiment of the invention;
[0031] FIG. 16 is an explanatory view showing a vicinity of a
groove of a repaired die, according to the modification of the
third embodiment of the invention;
[0032] FIG. 17 is a diagram explaining experimental results of a
life comparative test of repaired dies according to the first to
the third embodiments of the invention; and
[0033] FIG. 18 is a schematic diagram showing an enlarged view near
an opening of a groove formed on a die surface after forming a film
according to the modification of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Hereinafter are described first, second and third
embodiments of the present invention with reference to the
accompanying drawings.
(Die to be Repaired)
[0035] A description is given first, referring to FIGS. 1 to 3, on
a die 1 for molding a structure, which die is to be repaired using
a method of the present invention. The die 1 described hereinafter
is subjected to repairing throughout the first to the third
embodiments described later.
[0036] FIG. 1 is a partial perspective sectional view of the die 1
which is typically used for molding a structure. FIG. 2 is a
sectional view taken along line II-II' of FIG. 2. FIGS. 1 and 2
each show a state of a die before use.
[0037] As shown in FIGS. 1 and 2, the die 1 for molding a structure
(hereinafter referred to as "die 1") before use is made up of a die
body 11 in which supply holes 12 and grooves 13 are formed. The die
body 11 has a hole-formed surface 120 in which the supply holes 12
are formed and a groove-,formed surface 130 (also referred as a
first surface) in which the grooves 13 are formed. The hole-formed
surface 120 (also referred as a second surface) serves as a surface
for supplying a material to the die body 11. The groove-formed
surface 130 is an end face of the die body 11, through which a
material is extruded. The die body is made up of an SKD member.
[0038] The die 1 after use has the supply holes 12 for supplying a
material, and the grooves 13 arranged in a lattice form for
communicating with the supply holes 12 and for forming the material
into a desired shape. The die 1 after use also has corners 14 each
of which is formed at an intersecting line between the
groove-formed surface 130 having the grooves 13 and serving as an
end face of the die body 11, to which a material is extruded, and
an inner side face 131 of each of the grooves 13. As shown in FIG.
3, each of the corners 14 used to have a portion 19 before the die
1 is used, which, however, has disappeared through repeated use
(this portion is hereinafter referred to as "worn-out portion 19").
Typically, the corners 14 are largely worn out by being in contact
with a material. In FIG. 3, an initial form of the corner 14 is
indicated by a broken line. A region defined by the broken line and
the solid line in the figure corresponds to the worn-out portion
19. FIG. 3 illustrates a state of portion III of the die shown in
FIG. 2. It should be noted that FIG. 2 shows a die before use, and
FIG. 3 shows the die after use.
[0039] The die 1, which is to be repaired by using the repairing
method of the present invention, is used for molding a structure by
extruding a material containing a ceramics material, for example.
The worn-out portion 19 of the die 1 results from repeated use of
the die 1, or repeated extrusion of the material using the die 1.
As the abrasion progresses, formation of a structure having an
accurate dimension becomes difficult to eventually allowing the die
to come to the end of its lifetime.
[0040] As shown in FIG. 3, a depth D of the groove 13 is 5 mm. An
initial width "w" of the groove 13 before use is 140 .mu.m, and a
life-end width of the groove 13 is "w2" 150 .mu.m.
[0041] Each of the first to the third embodiments describes a
method for repairing the die one by restoring the worn-out portion
19, and a die repaired using the method.
First Embodiment
[0042] A method for repairing the die 1 according to a first
embodiment includes supplying a film-forming material onto the
worn-out portion 19 from the groove-formed surface 130, and
performing a PVD (physical vapor deposition) process to form a
repairing film 2. The method will now be explained with reference
to FIGS. 4 to 6.
(1.1 PVD Apparatus)
[0043] First of all, a PVD apparatus 5 used for the PVD process is
explained: As shown in FIG. 5, the PVD apparatus 5 has a
cylindrical reactor 51. The reactor 51 is made up of parts 51a,
51b, 51c, 51d and 51e. The reactor 51 has a diameter of 600 mm and
a height of 600 mm. A plurality of metal targets 52 are provided to
an inner side face 511 of the reactor 51. A pair of anode plates 53
are provided at positions next to a surface 521 of each metal
target 52. The pair of anode plates 53 are connected to a plus (+)
side of an arc power source, and the metal target 52 is connected
to a minus (-) side of the arc power source. In the present
embodiment, Cr or Ti is used as a material for constructing the
metal target 52.
[0044] As shown in FIG. 5, a rotating table 54 which is rotatable
about a vertical axis is provided at a bottom 512 of the reactor
51. The rotating table 54 is connected to a bias power source. A
top 513 of the reactor 51 is provided with a gas supply port 551
for supplying a reaction gas into the reactor 51 and an exhaust
port 552 for exhausting the gas in the reactor 51. The reactor 51
is also provided with a vacuum pump (not shown).
(1.2 Repairing Method)
[0045] The repairing method according to the present embodiment is
described below.
[0046] Prior to carry out the PVD process, a mask is provided to
the die 1 as shown in FIG. 4. Specifically, a masking plate 31 made
of graphite, for example, is laid over the hole-formed surface 120
so as to block the supply holes 12. Then, the die 1 and the masking
plate 31 are secured to a PVD jig 321. In this way, the hole-formed
surface 120 of the die 1 is masked.
[0047] Subsequently, the PVD process is carry out for the masked
die 1. As shown in FIG. 5, the PVD jig 321 to which the die 1 has
been secured is set on the rotating table 54, so that the
groove-formed surface 130 of the die 1 faces each of the metal
targets 52 as rotated by the rotating table 54. The reactor 51 is
then vacuumed, followed by heating. A degree of vacuum in the
reactor 51 is 1.times.10.sup.-6 Torr and a heating temperature is
500.degree. C. Then, N.sub.2, a reaction gas, is supplied to the
reactor 51 through the gas supply port 551.
[0048] As shown in FIG. 5, with each metal target 52 serving as a
cathode, arc discharge is allowed to occur at the surface 521 of
each metal target 52. Being encouraged by the energy of arc current
(70 to 200 A) generated by the arc discharge, the material
constructing each of the metal targets 52 instantaneously
evaporates and at the same time turns into metal ions 529, and then
flies into the reactor 51. Meanwhile, when a bias voltage is
applied to the PVD jig 321 through the rotating table 54 from a
bias power source, flying speed of the metal ions 529 is
accelerated. The metal ions 529, together with the particles of the
reaction gas (N.sub.2), turn into a film-forming material (CrN or
TiN in the present embodiment), collide against the groove-formed
surface 130 of the die 1, and deposit to form a film. In the
present embodiment, a film of an even thickness can be formed
because the PVD process is carry out with the rotation of the
rotating table 54.
[0049] Finally, after cooling the inside of the reactor 51, the
atmospheric condition is brought back and then the PVD jig 321 is
taken out of the reactor 51. Then, the PVD jig 321 is unsecured
from the repaired die 1.
[0050] In this way, as shown in FIG. 6, the repairing film 2 is
formed on the groove-formed surface 130 so as to extend onto each
corner 14 to restore the worn-out portion 19.
[0051] In the present embodiment, Cr was used for the metal target
52 to carry out the PVD process, and then the metal target 52 was
changed to the one made of Ti to again carry out the PVD process.
Accordingly, the repairing film 2 is made up of two layers, i.e. a
CrN layer and a TiN layer (not shown).
(1.3 Repaired Die)
[0052] Hereinafter is described a die repaired using the repairing
method according to the present embodiment.
[0053] As shown in FIG. 6, in the repaired die for molding a
structure according to the present embodiment, the repairing film 2
has been formed, through the PVD process, on the groove-formed
surface 130 so as to extend onto each corner 14 formed at an
intersecting line between the groove-formed surface 130 and the
inner side face 131 of the groove 13, so that the worn-out portion
19 is restored.
[0054] As mentioned above, the repairing film 2 consists of two
layers, i.e. the CrN layer and the TiN layer. The hardness of the
repaired film 2 is 2000 HV. As the hardness of the SKD member
making up the die body 11 is 500 HV, the hardness of the repairing
film is higher than that of the die body 11 by a factor of 4. In
order to obtain a repaired die for molding a honeycomb structure
having excellent durability and abrasion resistance, a repairing
film may preferably have a hardness larger than that of the main
body (500 HV). In particular, the repairing film may desirably have
a hardness higher than that of the main body by a factor of 1.5
(750 HV) or more to serve as a good coating film for satisfying the
required function. The repairing film 2 well satisfies the required
function. It should be noted that a width w3 of the groove 13 in
the repaired die 1 is 140 .mu.m.
[0055] FIG. 7 shows a relation between a depth "d" from the
groove-formed surface 130 along a direction in which the groove 13
extends and a thickness "t" of the repairing film 2. Specifically,
as shown in FIG. 6, the depth "d" is a distance from the
groove-formed surface 130 along a direction of the depth of the
groove 13, and the thickness "t" is a thickness of the repairing
film 2 along a direction parallel to the groove-formed surface
130.
[0056] As can be seen from FIG. 7, at the position of a depth d=0.5
mm, the thickness "t" is close to "0". This indicates that a region
d1 (refer to FIG. 6) in which the repairing film 2 is formed
extends within the length or 0.5 mm. In other words, the repairing
film 2 is formed in a region which is equal to or smaller than one
tenth of a depth D (=5 mm) of the groove 13. It should be
appreciated that the region d1 for forming the repairing film 2 is
to extend from the groove-formed surface 130 to the point where the
thickness "t" of the repairing film 2 is substantially "0".
[0057] FIG. 8 shows a relation between a distance L from the inner
side face 131 of the groove 13 along a direction in which the
groove-formed surface 130 extends (refer to FIG. 6), and a
thickness "s" of the repairing film 2. Specifically, as shown in
FIG. 6, the distance L is a distance along a direction stepping
away from the inner side face 131 of the groove 13. The thickness
"s" is a thickness of the repairing film 2 which is formed in a
direction opposite to the depth of the groove 13. It should be
noted that the depth of the groove 13 is measured with the
groove-formed surface 130 before use as a reference surface X. As
can be seen from FIG. 8, the thickness of the repairing film 2
falls within the range of 3 to 4 .mu.m.
(1.4 Advantages)
[0058] The following is a description on the advantages of the
repairing method according to the present embodiment.
[0059] In the method for repairing the die 1 for molding a
structure, the repairing film 2 is formed, through the PVD process,
on the groove-formed surface 130 so as to extend onto each of the
corners 14 to restore the worn-out portion 19, as described above.
Particularly, the repairing film 2 is formed, through the PVD
process, only on the side of the groove-formed surface 130 which
serves as a surface for extruding a material and plays the most
important roll for determining the moldability and dimensional
accuracy of a structure.
[0060] Thus, in comparison with the conventional repairing method
in which a repairing process is carried out with respect to the
entire die, the inventive repairing process can be readily and
efficiently carried out, and the repairing film 2 can be formed
with good accuracy. In addition, film-forming accuracy of the PVD
process is so high that the repairing film 2 can be formed with
much higher accuracy than in the conventional method. Further, the
PVD process can form so thick a film that the repairing process for
the die 1 can be performed more efficiently.
[0061] As described above, the worn-out portion 19 of each corner
14 can be readily restored with good accuracy. In other words, the
life-ended die 1 can be repaired to an extent that the repaired die
1 can mold a structure whose accuracy is equivalent to that of the
structure molded by the initial-state die 1.
[0062] The repairing film 2 formed by the PVD process has high
density and high hardness. By forming such a repairing film on the
groove-formed surface 130 for extruding a material therefrom, so as
to extend onto each corner 14 tending to suffer from abrasion to
thereby restore the worn-out portion 19, the repaired die 1 can
effectively achieve excellent durability and abrasion
resistance.
[0063] As mentioned above, the repairing film 2 of the present
embodiment is made up of multiple layers of TiN and CrN, and the
hardness of the repairing film 2 is 2000 HV, which is higher than
that of the die body 11 by a factor of 4. This means that the
repairing film 2 becomes very hard, whereby the repaired die 1 can
achieve sufficient durability and abrasion resistance.
[0064] The repairing film 2 may alternatively be made up of a
single layer of TiN or CrN. A single layer of TiN or a single layer
of CrN is still capable of maintaining hardness to a degree of 500
HV or higher, preferably 750 HV or more, as described above, which
is the hardness required for serving as a good coating film.
[0065] The repairing film 2 is formed depthwise of each groove 13
starting from the groove-formed surface 130, so as to extend within
a region which is one tenth or less of the depth D of the groove
13. This exerts an effect of suppressing unevenness in the width of
the grooves 13 in the repaired die 1. As a result, the dimensional
accuracy of a structure molded by the repaired die 1 can be
enhanced.
[0066] As described above, in the method for repairing a die
according to the present embodiment, a die for molding a structure
can be readily repaired with good accuracy, and thus a repaired die
for molding a structure may exert excellent durability and abrasion
resistance.
(1.5 Modification)
[0067] In the first embodiment, the side of the hole-formed surface
120 of the die body 11 has been masked because a plurality of metal
targets 52 have been provided in the PVD apparatus 5.
Alternatively, no mask may be provided to the die 1 in the case
where, for example, a single metal target 52 is provided, with the
die 1 being set so that the metal target 52 and the groove-formed
surface 130 of the die 1 face with each other and with the relative
position of the both being fixed while the PVD process is carried
out.
[0068] Although Cr or Ti has been used for the metal target 52 in
the first embodiment, the repairing film 2 can be formed using
other metal.
Second Embodiment
[0069] Referring now to FIGS. 1-3, 6-8, 9 and 10, hereinafter is
described a method for repairing a die for molding a structure and
a die repaired by using a repairing method according to a second
embodiment of the invention. In the present embodiment, the
identical or similar components or processes are given the same
references for the sake of simplification or omission of
explanation.
[0070] As shown in FIG. 9, in the method for repairing the die 1
according to the present embodiment, a mask is provided to the
hole-formed surface 120 formed with the supply holes and serving as
a surface for supplying a material to the die body 11, so that the
supply holes 12 are blocked. Subsequently, a film-forming material
is supplied from the side of the groove-formed surface 130 formed
with the grooves 13 and serving as an end surface of the die body
11, through which a material is extruded, followed by carrying out
a CVD (chemical vapor deposition) process, so that the repairing
film 2 is formed on the groove-formed surface 130, extending onto
each corner 14 at the intersecting line between the groove-formed
surface 130 and the inner side face 131 of the groove 13, thereby
restoring a worn-out portion (worn-out portion 19).
[0071] It should be appreciated that the die 1 repaired using the
repairing method of the present embodiment has the same quality and
shape (refer to FIGS. 1 to 3) as those of the die 1 repaired in the
first embodiment.
(2.1 CVD Apparatus)
[0072] With reference to FIG. 10, a CVD apparatus 4 used for the
CVD process is described below.
[0073] The CVD apparatus 4 has a cylindrical reaction furnace 41
with an open bottom and has a diameter of 450 mm and a height of
700 mm. A box-shaped reactor 42 is disposed in the reaction furnace
41. The reactor 42 is provided therein with a shelf 43 in which a
plurality of chambers are defined for locating the dies 1 to be
subjected to the CVD process.
[0074] A gas supply port 441 for providing a reaction gas into the
reactor 42 is provided at a bottom 422 of the reactor 42. The gas
supply port 441 is connected to an externally provided gas supply
apparatus 46 through a gas supply pipe 442. The CVD apparatus 4 is
arranged in such a way that the reaction gas can be supplied into
the reactor 42 from the gas supply apparatus 46. In the present
embodiment, TiCl.sub.4, H.sub.2, Ar, CH.sub.4 or N.sub.2 is used as
a reaction gas to be supplied from the gas supply apparatus 46.
[0075] An exhaust port 451 for exhausting a gas out of the reactor
42 is provided at the bottom 422 of the reactor 42. The exhaust
port 451 is connected to an exhaust pipe 452 which extends from the
proximity of a top 423 of the reactor 42 to the bottom 422. The CVD
apparatus 4 is arranged such a way that the gas in the reactor 42
can be discharged from the exhaust port 451 after being sucked from
a suction port 453.
(2.2 Repairing Method)
[0076] The repairing method of the present embodiment will now be
described in detail below.
[0077] Prior to carrying out the CVD process, a mask is provided to
the die 1. As shown in FIG. 9, the masking plate 31 made of
graphite, for example, is laid over the hole-formed surface 120 so
as to block the supply holes 12. Then, the die 1 and the masking
plate 31 are secured to a CVD jig 322. In this way, the hole-formed
surface 120 of the die 1 is masked.
[0078] Subsequently, the CVD process is carried out for the masked
die 1. As shown in FIG. 10, the CVD jig 322 to which the die 1 has
been secured is set on the shelf 43, so that the groove-formed
surface 130 of the die 1 faces the top 423 of the reactor 42 and
that the reaction gas is readily brought into contact with the
groove-formed surface 130 of the die 1. Then, the inside of the
reactor 42 is heated up to 900 to 1000.degree. C., followed by
supplying TiCl.sub.4, H.sub.2, Ar, CH.sub.4 and N.sub.2 as reaction
gases into the reactor 42 from the gas supply apparatus 46.
[0079] As shown in FIG. 10, the die body 11 heated up to high
temperature comes into contact with the reaction gases circulating
in the reactor 42 to cause chemical reaction above the
groove-formed surface 130 of the die body 11. Thus composed
film-forming materials (TiC, TICN and TiN in the present
embodiment) are deposited on the groove-formed surface 130 to form
a film.
[0080] Finally, the inside of the reactor 42 is cooled down to take
out therefrom the CVD jig 322. Then, the CVD jig 322 is unsecured
from the repaired die 1.
[0081] As described above, the repairing film 2 is formed, as in
the first embodiment, on the groove-formed surface 130 so as to
extend onto each corner 14 to restore the worn-out portion 19 as
shown in FIG. 6. In the present embodiment, the repairing film 2 is
made up of three layers, i.e. a TiC layer, a TICN layer and a TiN
layer (not shown).
(2.3 Repaired Die)
[0082] Hereinafter is described the die 1 repaired by the repairing
method of the present embodiment.
[0083] As shown in FIG. 6, the repairing film 2 is formed by
utilizing the CVD process on the groove-formed surface 130 so as to
extend onto each corner 14 to restore the worn-out portion 19 in
the repaired die 1 for molding a structure.
[0084] As described above, the repairing film 2 is made up of three
layers, i.e. the TiC layer, the TiCN layer and the TiN layer. The
hardness of the repairing film 2 is 2000 HV, which is higher than
that of the die body 11 by a factor of 4. A width w3 of each groove
13 is 140 .mu.m.
[0085] The physical characteristics of the repairing film obtained
in the second embodiment are substantially the same as those of the
repairing film in the first embodiment (refer to FIGS. 6 to 8).
(2.4 Advantages)
[0086] The following is a description on the advantages of the
repairing method according to the present embodiment.
[0087] In the method for repairing the die 1 for molding a
structure according to the present embodiment, the repairing film 2
is formed, through the CVD process, only on the side of the
groove-formed surface 130, which serves as a surface for extruding
a material in molding a structure and plays the most important roll
for determining the moldability and dimensional accuracy of the
structure.
[0088] Thus, in comparison with the conventional method in which a
repairing process is given to the entire die, the die 1 can be
efficiently repaired by the inventive method, and at the same time,
the repairing film 2 can be formed with good accuracy.
[0089] As described above, the worn-out portion 19 of each corner
14 can be readily restored with good accuracy. In other words, the
life-ended die 1 can be repaired to an extent that the repaired die
1 can mold a structure whose accuracy is equivalent to that of the
structure molded by the initial-state die 1. The repairing film 2
formed by the CVD process has high density and high hardness. By
forming such a repairing film on the groove-formed surface 130 for
extruding a material therefrom, so as to extend onto each corner 14
tending to cause abrasion to thereby restore the worn-out portion
19, the repaired die 1 can effectively achieve excellent durability
and abrasion resistance.
[0090] The CVD process has an effect of enhancing adhesion of the
repairing film to a base member (which corresponds to the die body
11 in the present embodiment), and thus much more excellent
durability can be achieved.
[0091] Further, as described above, the repairing film 2 is made up
of multiple layers of TiC, TiCN and TiN. This means that the
repairing film 2 is turned into one having higher hardness, whereby
the repaired die 1 can achieve much more excellent durability and
abrasion resistance.
[0092] It should be appreciated that other advantages are the same
as those in the first embodiment.
(2.5 Modification)
[0093] In the second embodiment, the repairing film 2 has been made
up of the multiple layers of TiC, TiCN and TiN. Alternatively, the
repairing film 2 may be structured by a single layer of TiC, TiCN
or TiN. Alternatively, the repairing film 2 may be structured by
two layers formed of any combination of two materials among TiC,
TiCN and TiN. In these alternatives as well, it is possible to
obtain a repairing film having a hardness of 500 HV, preferably 750
HV or more, which is the hardness required as a good coating film
as described above.
3. Third Embodiment
[0094] Referring now to FIGS. 1-5 and 10-13, hereinafter is
described a method for repairing a die for molding a structure, and
a die repaired by using the repairing method, according to a third
embodiment of the present invention. In the present embodiment, the
identical or similar components or processes are given the same
references for the sake of simplification or omission of
explanation.
[0095] In the method for repairing the die 1 according to the
present embodiment, a CVD repairing film 21 is formed by using the
CVD process on the groove-formed surface 130 formed with the
grooves 13 and serving as and end surface of the die body 11,
through which extrusion is performed, the CVD repairing film 21
extending onto each corner 14 at an intersecting line between the
groove-formed surface 130 and the inner side face 131 of each
groove 13 (refer to FIG. 3) to make up for the worn-out portion 19.
Subsequently, a film-forming material is supplied from the side of
the groove-formed surface 30 onto the CVD repairing film 21 that
has been formed on the groove-formed surface 130 so as to extend
onto the corner 14. Then the PVD process is carried out to thereby
form a PVD repairing film 22 on the CVD repairing film 21 to make
up for the worn-out portion 19. In this way, the worn-out portion
19 at each of the corners 14 can be restored.
(3.1 CVD Apparatus and PVD Apparatus)
[0096] It should be appreciated that the CVD apparatus and the PVD
apparatus used in the third embodiment are the same as the ones
used in the second embodiment and the first embodiment,
respectively.
(3.2 Repairing Method)
[0097] The repairing method of the present embodiment is described
in detail below.
[0098] After masking the die 1, the CVD process is carried out.
[0099] As shown in FIG. 9, the masking plate 31 made of graphite,
for example, is laid over the hole-formed surface 120 so as to
block the supply holes 12. Then, the die 1 and the masking plate 31
are secured to the CVD jig 322. In this way, the hole-formed
surface 120 of the die 1 is masked.
[0100] Then, as shown in FIG. 10, the CVD jig 322 to which the die
1 is secured is set on the shelf 43, so that the groove-formed
surface 130 of the die 1 faces the top 423 of the reactor 42 and
that the reaction gas is readily brought into contact with the
groove-formed surface 130 of the die 1. Then, the inside of the
reactor 42 is heated up to 900 to 1000.degree. C., followed by
supplying TiCl.sub.4, H.sub.2, Ar, CH.sub.4 and N.sub.2 as reaction
gases into the reactor 42 from the gas supply apparatus 46.
[0101] As shown in FIG. 10, the die body 11 heated up to high
temperature comes into contact with the reaction gases circulating
in the reactor 42 to cause chemical reaction above the
groove-formed surface 130 of the die body 11. Thus formed
film-forming materials (TiC, TiCN and TiN in the present
embodiment) are deposited on the groove-formed surface 130 to form
a film.
[0102] Finally, the inside of the reactor 42 is cooled down to take
out therefrom the CVD jig 322. Then, the CVD jig 322 is unsecured
from the repaired die 1. Thus, the CVD repairing film 21 is formed,
as shown in FIG. 8, on the groove-formed surface 130 so as to
extend onto each corner 14 to restore the worn-out portion 19. In
the present embodiment, the CVD repairing film 21 is made up of
three layers, i.e. a TiC layer, a TiCN layer and a TiN layer (not
shown).
[0103] Subsequently, after masking the die 1 that has been
subjected to the CVD process, the PVD process is carried out. As
shown in FIG. 4, the masking plate 31 made up of graphite, for
example, is laid over the hole-formed surface 120 so as to block
the supply holes 12. Then, the die 1 and the masking plate 31 are
secured to the PVD jig 321. In this way, the side of the
hole-formed surface 120 of the die 1 is masked.
[0104] Then, as shown in FIG. 5, the PVD jig 321 to which the die 1
is secured is set on the rotating table 54, so that the
groove-formed surface 130 of the die 1 faces each of the metal
targets 52 as the rotating table 54 rotates. The reactor 51 is then
heated after its inside has been vacuumed. A degree of vacuuming
the inside of the reactor 51 is 1.times.10.sup.-6 Torr and the
heating temperature is 500.degree. C. As a reaction gas, N.sub.2 is
supplied into the reactor 51 from the gas supply port 551.
[0105] As shown in FIG. 5, with each metal target 52 serving as a
cathode, arc discharge is allowed to occur at the surface 521 of
each metal target 52. Being encouraged by the energy of arc current
(70 to 200 A) generated by the arc discharge, the material
constructing each of the metal targets 52 instantaneously
evaporates and at the same time turns into metal ions 529, and then
flies into the reactor 51. Meanwhile, when a bias voltage is
applied to the PVD jig 321 through the rotating table 54 from a
bias power source, the speed of the metal ions 529 that have flown
out is accelerated. The metal ions 529, together with the particles
of the reaction gas (N.sub.2), turn into film-forming materials
(CrN and TiN in the present example), collide against the
groove-formed surface 130 of the die 1, and deposit to form a film.
In the present embodiment, a film of an even thickness can be
formed because the PVD process is carried out while the rotating
table 54 is rotated.
[0106] Finally, after cooling the inside of the reactor 51, the
atmospheric condition is brought back and then the PVD jig 321 is
taken out of the reactor 51. Then, the PVD jig 321 is unsecured
from the repaired die 1.
[0107] In this way, as shown in FIG. 11, the PVD repairing film 22
is formed on the CVD repairing film 21 that has been formed on the
groove-formed surface 130 so as to extend onto each corner 14 to
restore the worn-out portion 19.
[0108] In the present embodiment, Cr is used for the metal target
52 to carry out the PVD process, and then the metal target 52 is
changed to the one made of Ti to again carry out the PVD process.
Accordingly, the PVD repairing film 22 is made up of two layers,
i.e. a CrN layer and a TiN layer (not shown).
(3.3 Repaired Die)
[0109] The repaired die 1 obtained by the repairing method of the
present embodiment is now described.
[0110] As shown in FIG. 11, in the die 1 for molding a structure
according to the present embodiment, the CVD repairing film 21
formed by carrying out the CVD process is provided on the
groove-formed surface 130 formed with the grooves 13 and serving as
the end surface of the die body 11, through which a material is
extruded, the CVD repairing film 21 extending onto each corner 14
at the intersecting line between the groove-formed surface 130 and
the inner side face 131 of each groove 13 to make up for the
worn-out portion 19.
[0111] Further, the PVD repairing film 22 formed by carrying out
the PVD process is provided on the CVD repairing film 21 that has
been provided on the groove-formed surface 130 so as to extend onto
each corner 14 to make up for the worn-out portion 19. In this way,
the worn-out portion 19 at each of the corners 14 can be
restored.
[0112] As shown in FIG. 11, the width w3 of the groove 13 of the
repaired die 1 is 140 .mu.m.
[0113] As described above, the CVD repairing film 21 is made up of
three layers, i.e. the TiC layer, the TiCN layer and the TiN layer,
and has the hardness 2000 HV. As the hardness of the SKD member
constructing the die body 11 is 500 HV, the hardness of the CVD
repairing film 21 is higher than that of the die body 11 by a
factor of 4.
[0114] Further, the PVD repairing film 22 is made up of two layers,
i.e. the CrN layer and the TiN layer as described above.
[0115] The hardness of the CVD repairing film 21 is 2000 HV, which
is higher than that of the die body 11 by a factor of 4.
[0116] FIG. 12 shows a relation between the depth "d" from the
groove-formed surface 130 along the direction in which the groove
13 extends and the total thickness "t" of the two repairing films
21 and 22. FIG. 12 also shows the thickness of the CVD repairing
film 21 alone. As shown in FIG. 11, the depth "d" is a distance
from the groove-formed surface 130 along the direction of depth of
the groove 13, and the thickness "t" is the total thickness of the
repairing films 21 and 22 along the direction parallel to the
groove-formed surface 130.
[0117] As can be seen from FIG. 12, at the position of a depth
d=0.5 mm, the thickness of the PVD repairing film 22 is close to
"0". This indicates that the region d1 (refer to FIG. 11) in which
the PVD repairing film 22 is formed extends within a length of 0.5
mm. In other words, the PVD repairing film 22 is formed in a region
which is equal to or smaller than one tenth of the depth D (=5 mm)
of the groove 13. It should be appreciated that the region d1 for
forming the PVD repairing film 22 is to extend from the
groove-formed surface 130 to the point where the thickness "t" of
the PVD repairing film 22 is substantially "0".
[0118] FIG. 13 shows a relation between the distance L from the
inner side face 131 of the groove 13 along the direction in which
the groove-formed surface 130 extends and the total thickness "s"
of the two repairing films 21 and 22. FIG. 13 also shows the
thickness of the CVD repairing film 21 alone. As shown in FIG. 11,
the distance L is a distance in the direction stepping away from
the inner side face 131 of the groove 13. The thickness "s" is the
total thickness of the two repairing films 21 and 22 measured with
the original groove-formed surface 130 as a reference surface
X.
[0119] As can be seen from FIG. 13, the total thickness of the
repairing films 21 and 22 falls within the range of 6 to 8 .mu.m.
Of the total thickness, the thickness of the CVD repairing film 21
occupies a thickness ranging from 1 to 2 .mu.m.
(3.4 Advantages)
[0120] The following is a description on the advantages of the
repairing method according to the present embodiment.
[0121] In the method for repairing the die 1 for molding a
structure according to the present embodiment, the CVD repairing
film 21 is formed through the CVD process on the groove-formed
surface 130 so as to extend onto each corner 14 to restore the
worn-out portion 19. Subsequently, the PVD repairing film 22 is
formed through the PVD process on the CVD repairing film 21 that
has been formed on the groove-formed surface 130 so as to extend
onto each corner 14 to restore the worn-out portion 19. In other
words, both of the CVD and the PVD processes are performed on the
side of the groove-formed surface 130 which serves as a surface for
extruding a material therefrom and plays the most important roll in
determining the moldability and dimensional accuracy of a
structure, so that both of the CVD repairing film 21 and the PVD
repairing film 22 are formed.
[0122] In this way, the worn-out portion 19 of each corner 14 can
be readily restored with good accuracy. In other words, the
life-ended die 1 can be repaired to an extent that the repaired die
1 can mold a structure whose accuracy is equivalent to that of the
structure molded by the initial-state die 1.
[0123] The two repairing films 21 and 22 formed by both of the
processes have high density and high hardness. By forming two such
repairing films 21 and 22 on the groove-formed surface 130 for
extruding a material so as to extend onto each corner 14 tending to
cause abrasion to thereby restore the worn-out portion 19, the
repaired die 1 can effectively achieve excellent durability and
abrasion resistance.
[0124] The CVD repairing film 21 formed by the CVD process exerts
high adhesion to the base member (which corresponds to the die body
11 in the present embodiment). Therefore, formation of such a CVD
repairing film 21 as a base can much more enhance the durability of
the repaired die 1.
[0125] The PVD repairing film 22 formed by the PVD process has high
film-forming accuracy. Because such a PVD repairing film 22 is
formed as an upper layer of the repairing film of the double
structure, which is formed on the side of the groove-formed surface
130, dimensional accuracy of the repaired die 1 is ensured to
become much higher. Therefore, moldability and dimensional accuracy
can be more enhanced in the structure obtained by using the
repaired die 1.
[0126] The PVD process can readily achieve formation of a thick
film. Accordingly, comparing with the conventional case where only
the CVD process is used, which is unlikely to achieve formation of
a thick film, the method of the present embodiment can readily form
a repairing film having a sufficient thickness for restoring the
worn-out portion of the die 1. Thus, the repairing process of the
die 1 can be performed with efficiency.
[0127] In the present embodiment, the CVD repairing film 21 is made
up of a multiple layers of TiC, TiCN and TiN. Therefore, the CVD
repairing film 21 has high hardness and can enhance adhesion to the
die body 11. Thus, the repaired die 1 can achieve sufficient
durability and abrasion resistance.
[0128] Further, the PVD repairing film 22 is made up of a multiple
layers of TiN and CrN. Therefore, the PVD repairing film 22 has
high hardness, so that the repaired die 1 may have sufficient
durability and abrasion resistance.
[0129] Further, the PVD repairing film 22 is formed in a region
which is equal to or smaller than one tenth of the depth D of the
groove 13 starting from the groove-formed surface 130. Thus,
unevenness of the width of each groove 13 can be suppressed in the
repaired die 1. Therefore, the dimensional accuracy of the
structure molded by using the repaired die 1 can be enhanced.
[0130] The hardness of the CVD repairing film 21 and the PVD
repairing film 22 is 2000 HV which is higher than that of the die
body 11 by a factor of 4. As a result, the two repairing films 21
and 22 exert high hardness, whereby the repaired die 1 may achieve
sufficient durability and abrasion resistance.
[0131] As described above, by using the method for repairing a die
according to the present embodiment, a die for molding a structure
can be readily repaired with good accuracy, and thus the repaired
die for molding a structure may have excellent durability and
abrasion resistance.
(3.5 Modification)
[0132] In the third embodiment, the CVD repairing film 21 has been
made up of a multiple layers of TiC, TiCN and TiN. Alternatively,
the CVD repairing film 21 may be made up of a single layer of any
one of TiC, TiCN and TiN, or may be made up of two layers formed of
any combination of two materials among TiC, TiCN and TiN. Further,
although the PVD repairing film 22 has been made up of a multiple
layers of TiN and CrN in the third embodiment, it may be made up of
a single layer made up of either one of TiN and CrN. In any of
these alternatives, it is possible to obtain a repairing film
having a hardness larger than 500 HV, preferably 750 HV or more,
which is a hardness required as a good coating film as described
above.
[0133] The best moldability and dimensional accuracy of a structure
are attained by the groove-formed surface 130, especially, an
opening width and shape of the grooves 13 thereon. Accordingly, in
repairing a used die, it is essential to provide a repairing film
on the groove-formed surface 130 so as to extend onto each corner
14 to restore the worn-out portion 19, assuring the grooves 13 to
have the width w3. However, the repairing film may be or may not be
provided to the portions other than the groove-formed surface 130.
For example, in the repairing method in the third embodiment, the
CVD process and the PVD process may be performed without providing
a mask as described below.
[0134] As shown in FIG. 14, in the repairing method of the present
modification, the die 1 is secured to the CVD jig 322. Then, by
using the CVD apparatus 4 shown in FIG. 10, the CVD process is
carried out. Thus, as shown in FIG. 16, the CVD repairing film 21
can be formed over the die body 11.
[0135] Subsequently, as shown in FIG. 15, the die 1 is secured to
the PVD jig 321. Then, the PVD process is carried out using the PVD
apparatus 5 shown in FIG. 5. In this case, in performing the PVD
process, a single metal target 52 is provided in the PVD apparatus
5, and the die 1 is set so that the metal target 52 faces the
groove-formed surface 130 of the die 1, and further, the die 1 and
the metal target 52 are fixedly positioned. Thus, as shown in FIG.
16, the PVD repairing film 22 is formed on the CVD repairing film
21 that has been formed on the groove-formed surface 130 so as to
extend onto each corner 14 to restore the worn-out portion 19.
[0136] Other procedure, arrangement and advantages are the same as
in the third embodiment.
4. Lifetime Evaluation
[0137] A honeycomb structure was repeatedly formed using a repaired
die 10 obtained through the methods of the first, the second and
the third embodiments to evaluate the lifetime of the dies.
(4.1 Samples for Comparative Evaluation)
[0138] As the inventive articles, the die 10 repaired by the PVD
process according to the first embodiment (Inventive Article E1),
the die 10 repaired by the CVD process according to the second
embodiment (Inventive Article E2) and the die 10 repaired by both
the CVD process and the PVD process according to the third
embodiment (Inventive Article E3) were prepared. As comparative
articles, an unused initial die with no treatment (Comparative
Article C1) was prepared. In all of these dies, the width of the
groove 13 was set at 140 .mu.m.
(4.2 Procedure for Evaluation)
[0139] The procedure of evaluation is as follows.
[0140] Using the dies 10 of Inventive Articles E1, E2 and E3,
extrusion was performed using a material containing cordierite
ceramic to form honeycomb structures. The molded honeycomb
structures each had a cylindrical shape with a diameter 100 mm and
a length 90 mm. Extrusion was repeatedly performed. When the width
of the groove 13 in the groove-formed surface 130 became 150 .mu.m
or more, the die was determined to have ended its lifetime. The
same procedure was taken as to Comparative Article C1. The number
of honeycomb structures produced by each die up to the end of its
lifetime was counted. A production ratio of each of Inventive
Articles E1, E2 and E3 was calculated with the number of honeycomb
structures produced by using Comparative Article C1 as a reference
production ratio "1".
(Evaluation Results)
[0141] Results of the evaluation are shown in FIG. 17.
[0142] As can be seen from the figure, the production ratio of
Inventive Article E1 repaired by the PVD process was twice as high
as that of unused/unprocessed Comparative Article C1. Further, the
production ratios of Inventive Article E2 repaired by the CVD
process and Inventive Article E3 repaired by both of the PVD
process and the CVD process were each three times as high as that
of Comparative Article C1. In other words, it can be seen that
Inventive Articles E1, E2 and E3 each exerted quite excellent
durability and abrasion resistance and the die's lifetime was
longer.
5. Further Modification
[0143] As described above, the production ratios of Inventive
Articles E1, E2 and E3 are each higher than that of Comparative
Article C1 by a factor of 2 or 3.
[0144] Accordingly, dies may be manufactured employing the
repairing method of the present invention. Specifically,
Comparative Article C1 may be provided with etching or grinding
treatment (also referred as pre-treatment) first, for example, to
purposely form a die having the worn-out portion 19 whose worn-out
degree is substantially the same as that of the dies repaired
through the methods of the first, second and third embodiments and
the modification. Subsequently, the repairing method of the first,
second or third embodiment may be performed for the resultant
etched or grinded die. This procedure may be applied as a method
for manufacturing a die (i.e. surface treatment method for forming
grooves in a die), and a die manufactured in this way may exert
excellent durability and abrasion resistance.
[0145] As shown in FIG. 18, from the manufacturing process view,
the pre-treatment, namely a rounding process for rounding an
original sharp corner 14A and 14B, contributes to ensure
dimensional accuracy in an opening width w1 of the groove 13.
[0146] Namely, if the film 2 is formed on the Article C1 which has
the original sharp corners 14A and 14B, an overhang w4 and w5 will
be formed. These overhangs cause a dimensional error (i.e.,
w1-w3=w1-w4-w5) in the opening width of the groove. This
dimensional error degrades durability of a processed die and
dimensional accuracy of the structural body manufactured by using
the processed die. In contrast, the film 2 formed on the Article C1
which is pre-treated and has a rounding corner, similar to the
corner 14 shown in FIGS. 3, 6, and 11, hardly forms an overhang
similar to the overhang w4 and w5. In this way, forming a rounded
corner before forming a film thereon is preferable so as to
manufacture a die with good durability and accuracy and be capable
of mass-producing accurate structural bodies.
[0147] Further, this manufacturing method, and dies manufactured
using this manufacturing method should have all the advantages
obtained in the first, second and third embodiments and the
modification.
[0148] In order to explain the manner in which the present
invention exerts advantages, a specific method for repairing a used
die and a specific repaired die repaired thereby have been
described above. It will be appreciated, however, that the present
invention is not limited to these methods and repaired dies, but
any and all modifications, variations or equivalents, which may
occur to those who are skilled in the art, should be considered to
fall within the scope of the present invention.
* * * * *